1. Field of the Invention
The present invention relates to a functional copper (Cu) skin film, and particularly, to a skin film formed of an aggregate of Cu crystals.
2. Description of the Related Art
In a slide bearing for an internal combustion engine, which bearing is opposed to a rotary shaft, in order to prevent seizure and wearing due to fretting caused by a very small vibration or the like, it is conventionally known to form a Cu deposit layer, for example, on a back surface opposite from that surface of a backing made of a rolled sheet steel opposite the surface facing the rotary shaft.
However, the previously known Cu deposit layer has problems, under existing circumstances where speed and output of the internal combustion engine have tended to increase, such as the known Cu deposit layer is: not sufficient in oil retaining property, namely, oil retention due to a relatively smooth surface thereof; poor in seizure resistance because of a bad initial conformability; and low in wear resistance as a result of a local increase in surface pressure.
There is also a conventionally known graphite skin film formed by application on a surface of a work as an energy absorbing skin film in a laser machining.
However, the graphite skin film suffers from a problem that spots are liable to be produced, because the graphite skin film is formed by the application and as a result, it is difficult for the graphite skin film to exhibit a uniform energy absorbing ability over the whole thereof.